Lawrence Berkeley National Laboratory - Recent Work

Lawrence Berkeley National Laboratory
Recent Work

Title
Effective Kitchen Ventilation for Healthy Zero Net Energy Homes with Natural Gas

Permalink
https://escholarship.org/uc/item/6wg0f4ck

Authors
Singer, Brett
Chan, wanyu
Delp, William
et al.

Publication Date
2021

Peer reviewed

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 University of California

Energy Research and Development Division
FINAL PROJECT REPORT

Effective Kitchen
Ventilation for Healthy
Zero Net Energy Homes
with Natural Gas

Gavin Newsom, Governor
January 2021 | CEC-500-2021-005

PREPARED BY:
Primary Authors:
Brett C. Singer, Wanyu Rengie Chan, William W. Delp, Iain S. Walker, Haoran Zhao

Indoor Environment Group, Energy Technologies Area
Lawrence Berkeley National Laboratory
1 Cyclotron Road, Berkeley CA
510-486-4779
https://indoor.lbl.gov
https://eta.lbl.gov

Contract Number: PIR-16-012

PREPARED FOR:
California Energy Commission

Susan Wilhelm, Ph.D.
Project Manager

Jonah Steinbuck Ph.D.
Office Manager
ENERGY GENERATION RESEARCH OFFICE

Laurie ten Hope
Deputy Director
ENERGY RESEARCH AND DEVELOPMENT DIVISION

Drew Bohan
Executive Director

 DISCLAIMER
This report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily
represent the views of the Energy Commission, its employees or the State of California. The Energy Commission, the
State of California, its employees, contractors and subcontractors make no warranty, express or implied, and assume
no legal liability for the information in this report; nor does any party represent that the uses of this information will
not infringe upon privately owned rights. This report has not been approved or disapproved by the California Energy
Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in
this report.

ACKNOWLEDGEMENTS
The study team is deeply appreciative to the building managers and participants who enabled
the field work described in Chapter 2. The research team notes with appreciation the following
contributions to the field study: Toshifumi Hotchi prepared instrumentation and assisted with
data collection at Sites 1-2; Marion Russell supervised preparation and analysis of passive
samples; Yuhan Wang assisted with data analysis; Sebastian Cohn of the Association for
Energy Affordability led recruitment, scheduling, and implementation at the field sites. The
research team would like to thank Andrew Brooks of the Association for Energy Affordability
for subcontract administration and input to field study recruitment design. The research team
would also like to thank Yang-Seon Kim who did the first compilation of data from the HENGH
single-detached house study that contributed to the work presented in Chapters 2-3. The
research team also thanks Sangeetha Kumar for conducting the bulk of the simulation analysis
that is presented in Chapter 4.

The research team thanks the following individuals for their contributions to the project in their
service on the Technical Advisory Committee:
 • Marian Goebes, TRC Energy Services
 • Nicholas Hurst, United States Environmental Protection Agency Indoor Environments
 Division
 • Peggy Jenkins (retired), Indoor Exposure Assessment Section, California Air Resources
 Board
 • Kaz Kumagai, Indoor Air Quality Section Chief, California Department of Public Health
 • Michael Moore, P.E., Newport Ventures, Inc.
 • Jeff Miller, P.E., California Energy Commission
 • Russell Pope, Research and Development Manager, Panasonic Eco Solutions North
 America
 • James Sweeney, REEL Energy Systems Laboratory, Texas A&M University
 • Patrick Wong, Manager, Indoor Exposure Assessment Section, California Air Resources
 Board
 • Qunfang (Zoe) Zhang, Indoor Exposure Assessment Section, California Air Resources
 Board

Additional funding for this work was provided by the United States Department of Energy
Building America Program via Contract DE-AC02-05CH11231 and the United States
Environmental Protection Agency via Interagency Agreement DW-89-9232201-7.

 i

PREFACE
The California Energy Commission’s (CEC) Energy Research and Development Division
manages the Natural Gas Research and Development Program, which supports energy-related
research, development, and demonstration not adequately provided by competitive and
regulated markets. These natural gas research investments spur innovation in energy
efficiency, renewable energy and advanced clean generation, energy-related environmental
protection, energy transmission and distribution and transportation.
The Energy Research and Development Division conducts this public interest natural gas-
related energy research by partnering with RD&D entities, including individuals, businesses,
utilities and public and private research institutions. This program promotes greater natural
gas reliability, lower costs and increases safety for Californians and is focused in these areas:
 • Buildings End-Use Energy Efficiency.
 • Industrial, Agriculture and Water Efficiency
 • Renewable Energy and Advanced Generation
 • Natural Gas Infrastructure Safety and Integrity.
 • Energy-Related Environmental Research
 • Natural Gas-Related Transportation.
Effective Kitchen Ventilation in Healthy Zero Net Energy Homes with Natural Gas is the final
report for the Effective Kitchen Ventilation in Healthy Zero Net Energy Homes with Natural Gas
project (PIR-16-012) conducted by Lawrence Berkeley National Laboratory. The information
from this project contributes to the Energy Research and Development Division’s Natural Gas
Research and Development Program.
For more information about the Energy Research and Development Division, please visit the
CEC’s research website (www.energy.ca.gov/research/) or contact the CEC at 916-327-1551.

 ii

ABSTRACT
Past studies indicate that kitchen ventilation that minimally complies with California’s
Residential Building Code is inadequate at controlling combustion pollutants from natural gas
burners and particulate matter produced during cooking. Effectiveness is further limited by
misperceptions that kitchen ventilation is infrequently needed. This project developed the
technical basis for updating kitchen ventilation requirements to protect health in new California
homes, especially in smaller homes common among low-income renters. Tasks included (1) a
field study of ventilation equipment performance and indoor air quality in 23 low-income
apartments at four sites; (2) analysis of range hood use related to cooking time and household
parameters using data from 54 houses and 17 low-income apartments; (3) a measurement-
based study to quantify performance of over-the-range microwave ovens with integrated
exhaust fans; and (4) pollutant exposure simulations to inform capture efficiency standards.
The field study found operational deficiencies with mechanical ventilation systems in a
substantial fraction of low-income apartments that affected performance, resulting in higher
exposures to pollutants generated indoors. Using gas cooking burners produced high short-
term and weekly time-averaged nitrogen dioxide in apartments. Range hoods were used more
frequently with cooking in houses (36 percent) than apartments (28 percent); use increased
with overall cooking frequency in a home and with duration of cooktop but not oven events;
actual use was correlated to, but lower than, self-reported use; and use was more frequent in
houses when cooking generated any fine particulate matter (PM2.5) or when high PM2.5
resulted from cooking in apartments. Performance of over-the-range microwaves with
integrated exhaust fans was similar to that of range hoods of comparable price. Simulation
analysis found that performance standards need to be updated to ensure that kitchen exhaust
ventilation adequately protects for substantial cooking in new California residences.

Keywords: Air pollutant exposures; Building Energy Efficiency Standards; cooking; healthy
homes; indoor air quality; mechanical ventilation; residential.

Please use the following citation for this report
Singer, Brett C.; Wanyu Rengie Chan; William W. Delp; Iain S. Walker; Haoran Zhao. 2021.
 Effective Kitchen Ventilation for Healthy Zero Net Energy Homes with Natural Gas .
 California Energy Commission. Publication Number: CEC-500-2021-005.

 iii

iv

TABLE OF CONTENTS

ACKNOWLEDGEMENTS .........................................................................................................i
PREFACE ............................................................................................................................ ii
ABSTRACT ......................................................................................................................... iii
EXECUTIVE SUMMARY ........................................................................................................1
 Introduction .....................................................................................................................1
 Project Purpose ................................................................................................................3
 Project Approach ..............................................................................................................4
 Project Results .................................................................................................................5
 Technology/Knowledge Transfer/Market Adoption (Advancing the Research to Market) ........8
 Benefits to California ........................................................................................................8
CHAPTER 1: Introduction ................................................................................................. 11
CHAPTER 2: Field Study of Ventilation and Indoor Air Quality in New and Renovated Low-
Income Apartments........................................................................................................... 16
 Objective and Overview .................................................................................................. 16
 Approach ....................................................................................................................... 16
 Results .......................................................................................................................... 17
 Conclusions.................................................................................................................... 22
CHAPTER 3: Analysis of Range Hood Use Patterns in Homes with Gas Cooking Burners ........ 23
 Objective and Overview .................................................................................................. 23
 Approach ....................................................................................................................... 23
 Results .......................................................................................................................... 26
 Conclusions.................................................................................................................... 33
CHAPTER 4: Performance of Combined Over-the-Range Microwave and Exhaust Devices ...... 35
 Objective and Overview .................................................................................................. 35
 Background Relevant to Range Hood Performance ........................................................... 35
 Approach ....................................................................................................................... 37
 Results .......................................................................................................................... 43
 Conclusions.................................................................................................................... 47
CHAPTER 5: Pollutant Exposure Simulations to Inform Capture Efficiency Standards ............. 49
 Objective and Overview .................................................................................................. 49
 Approach ....................................................................................................................... 49

 v

Results .......................................................................................................................... 57
 Conclusions.................................................................................................................... 59
CHAPTER 6: Technology/Knowledge/Market Transfer Activities ............................................ 61
 Technical Support for California’s Building Energy Efficiency Standards .............................. 61
 Technical Support for Other Codes and Standards Related to Kitchen Ventilation ............... 62
 Technical support to other researchers studying air pollutant emissions and exposures in
 California homes. ........................................................................................................... 62
 Technical Papers and Reports and Presentations at Scientific Conferences ......................... 62
CHAPTER 7: Conclusions/Recommendations ....................................................................... 65
 Conclusions.................................................................................................................... 65
 Recommendations .......................................................................................................... 67
CHAPTER 8: Benefits to Ratepayers ................................................................................... 69
LIST OF ACRONYMS .......................................................................................................... 70
REFERENCES .................................................................................................................... 71

 LIST OF FIGURES
 Page
Figure 1: An Example of Full Range Hood Use During a Cooktop Event with Associated
Particulate Matter Emissions. ............................................................................................. 24
Figure 2: Distribution of Total Minutes of Cooktop and Oven Use Per Home Per Week at Each
Hour of the Day in Houses and Apartments ........................................................................ 27
Figure 3: Range Hood Use for All Cooking Events by Home ................................................. 28
Figure 4: Experiment Setup ............................................................................................... 40
Figure 5: Configuration to measure total airflow into OTR at Inlets ...................................... 41
Figure 6: Example of Airflow Measurement at Inside with Top Inlet Taped ........................... 42
Figure 7: Airflow Measured at Over the Counter Inlets versus Outlet .................................... 44
Figure 8: Capture Efficiency Related to Airflow for Over the Counter and Range Hoods in this
Study .............................................................................................................................. 46
Figure 9: Capture Efficiency and Range Hood Airflow from Past Lawrence Berkeley National
Laboratory Studies ............................................................................................................ 55
Figure 10: Capture Efficiency and Range Hood Airflow Determined Following the ASTM Test
Method............................................................................................................................. 56

 vi

LIST OF TABLES
 Page
Table 1: Selected Home Characteristics of Apartments in this Study and Houses in Previously
Published HENGH Study .................................................................................................... 18
Table 2: Air Pollutant Concentrations Over One Week in Apartments and Houses with Similar
Amounts of Cooking with Gas Burners ................................................................................ 19
Table 3: Range Hood Use by Cooking Type ........................................................................ 29
Table 4: Range Hood Use by Cooktop Use Duration ........................................................... 30
Table 5: Range Hood Use by Self-Reported Use Habit in Houses .......................................... 31
Table 6: Range Hood Use by Self-Reported Use Habit in Apartments ................................... 31
Table 7: Range Hood Use by Cooking Events with and without Fine Particulate Matter (PM 2.5)
Emissions ......................................................................................................................... 32
Table 8: Comparison of Over the Counter Models Tested with Models in HENGH Study ......... 38
Table 9: Over the Counter and Standard Range Hoods Tested ............................................. 39
Table 10: Measured Airflows (cfm) of 6 Over the Counter and 2 Range Hoods ...................... 45
Table 11: Model Input Parameters ..................................................................................... 52
Table 12: Percent of Homes exceeding PM2.5 24-h Threshold Value for Range Hoods with
ASTM Capture Efficiency and Modelled Airflow Rate as Drawn in Figure 10 ........................... 57
Table 13. Percent of Homes with 1h NO2 Exceeding the Threshold Value for Range Hoods with
the Same Capture Efficiency but Higher Flow Rates as Shown in Figure 9 for “two front
burners” ........................................................................................................................... 58
Table 14: Summary of ASTM Capture Efficiency or Range Hood Airflows Needed to Meet 24-h
Fine Particulate Matter Threshold Value .............................................................................. 59
Table 15: Summary of ASTM Capture Efficiency or Range Hood Airflows Needed to Meet 1-h
Nitrogen Dioxide Threshold Value of 100 Parts per Billion .................................................... 60

 vii

viii

EXECUTIVE SUMMARY
Introduction
California’s aggressive climate change mitigation policies include reducing greenhouse gas
emissions to 80 percent below 1990 levels by 2050 and achieving carbon neutrality by 2045.
Maximizing energy efficiency savings is a key element of achieving those goals while also
advancing energy affordability. For decades California has placed energy efficiency at the
center of its energy policies with energy codes, standards, and programs that have saved
Californians billions of dollars since the 1970s.
An airtight envelope is a core element of an energy efficient and resilient residential building.
Reducing uncontrolled air exchange with the outdoors reduces heating and cooling loads and
also enables better control of outdoor air pollution entry, which is particularly important during
wildfire events. For multiunit buildings, reducing air leakage between units reduces the
transfer of odors and pollutants and enables better control of thermal comfort and energy use.
However, there is a risk that reducing air leakage could also reduce annual average outdoor
air exchange as well as dilution and removal rates for air pollutants generated indoors, causing
an increase in chronic exposures if no other action is taken.
To protect indoor air quality in airtight homes, California’s Building Energy Efficiency
Standards, Part 6 of the Title 24 Building Code, require new homes to have mechanical
ventilation. The standards require: minimum airflow rates for ventilation to control long-term
exposure to continuously emitted pollutants throughout the home; kitchen exhaust to manage
odors, moisture and pollutants from cooking; and exhaust fans in bathrooms. The standards
are periodically updated in light of new information about performance needs and newly
available technologies and products.
Cooking is among the largest sources of air pollutant emissions inside many homes, with
substantial adverse health impacts. Gas cooking burners produce carbon monoxide (CO),
nitrogen dioxide (NO2), formaldehyde (HCHO), and ultrafine particles, while electric burners
generate ultrafine particles. Nitrogen dioxide from gas cooking burners may commonly reach
indoor concentrations that exceed the threshold of 100 parts per billion (ppb) over one hour
that is used in the United States ambient air quality standard. In a 2013 study, Belanger et al.
reported that higher residential exposures to NO2 are associated with asthma severity. In a
2013 meta-review, Lin et al. reported that gas cooking and higher NO2 exposure were each
associated with increased risk of asthma, and higher NO2 was associated with current wheeze,
a commonly used proxy for active asthma. High-temperature cooking activities (such as frying
and broiling) contribute odors and pollutants including hazardous organic gases, polycyclic
aromatic hydrocarbons, and fine and ultrafine particles. Higher exposures to these pollutants
are associated with adverse health effects. A study in Hong Kong, by Yu et al. in 2006,
reported a dose–response relationship between lifetime exposure to cooking fumes and lung
cancer.
Venting range hoods and combination “over the range” microwaves with integrated exhaust
fans (OTRs) are designed to remove some fraction of the emitted pollutants to outdoors
before they mix into the air volume of the kitchen and throughout the home. There are several
relevant measures of range hood performance. The two most commonly used, and the

 1

measures for which data are most readily available, are airflow and sound level that are
measured using standard test procedures published by the Home Ventilating Institute. The
Home Ventilating Institute certifies and publishes test results in a free online directory that
includes standard range hoods and over-the-range microwave and exhaust fan combined
devices mounted above the cooktop.
A third metric, for which more limited data are available, is capture efficiency. Capture
efficiency is the fraction of contaminants emitted at the cooktop that are directly pulled into
the range hood and exhausted to the outdoors before mixing throughout the house. A capture
efficiency of 100 percent means all cooking pollutants are exhausted directly to the outside,
and a capture efficiency of zero means that no cooking pollutants are directly exhausted,
allowing all of them to mix with indoor air. Capture efficiency was first studied decades ago
and the metric received increasing attention after Lawrence Berkeley National Laboratory used
it in studies conducted in the early 2010s. Several modeling and experimental studies have
examined the benefits of range hood use to reduce cooking-related indoor air pollution.
Research conducted by Lawrence Berkeley National Laboratory before this project, with range
hoods and OTRs in both laboratory and occupied home installations, found that capture
efficiency for a given device depends strongly on airflow, the type of cooking and whether
cooking is done on the front or back burners. The research team’s studies also found that
capture efficiency varies between devices. Also, based on just a few OTRs included in the
studies, it appeared that the capture efficiency performance of OTRs could be appreciably
lower than for range hoods at similar airflows.
Existing kitchen ventilation standards specify a minimum airflow and maximum sound rating at
the minimum airflow. For any exhaust device placed over the cooktop, the requirement is for a
minimum of 100 cubic feet per minute (cfm) of airflow at a maximum sound rating of 3 sones.
Kitchen ventilation alternately may be provided with a higher airflow intermittent exhaust fan
or a continuous exhaust fan in the kitchen. California’s Building Energy Efficiency Standards
require that the airflow of installed kitchen exhaust equipment must either be verified by
onsite measurement or assured through use of a product that has had its airflow measured
and certified by an approved testing and certification process. The approach of using a
certified product also requires ducting that complies with prescriptive requirements. Until
recently, the only organization approved by the state to certify range hood airflow
measurements was the Home Ventilating Institute.
Recognizing that airflow is too coarse and imprecise a measure for range hood effectiveness,
an effort was initiated in the mid-2010s to develop a standard test method for range hood
capture efficiency. The intent was to establish a testing and certification system analogous to
those existing for airflow and sound. Lawrence Berkeley National Laboratory conducted
research to support this effort and the standard was developed through ASTM International (a
standards organization formerly known as American Society for Testing and Materials),
resulting in Method E3087. This method was developed to be repeatable and represent
emissions from the burner and cooking.
The airflow of a range hood installed in a home can differ from the value published by the
Home Ventilating Institute for several reasons, and airflows measured from range hoods in
homes have often been lower than rated values.

 2

Compared to standard range hoods, OTRs present a greater challenge for determining airflow
as installed. When configured to operate in recirculation mode, air is drawn into OTRs through
inlets on the underside and expelled through vents at the top and front, above the door. When
configured to exhaust air to the outdoors (venting mode), air enters through openings at the
bottom and above the door and is expelled through an opening at the top or back. The OTR
flow dynamics complicate the measurement of airflow when there is no access to the outlet.
A recent California Energy Commission (CEC) funded field study of 70 single-detached homes
built to comply with the state’s mechanical ventilation requirements found that almost all of
the homes had general mechanical ventilation equipment that met the requirements of
California’s Building Energy Efficiency Standards. Measurements during a one-week period in
each home, with the general mechanical ventilation systems operating, found that
concentrations of several measured air pollutants were generally low and few homes had
pollutant concentrations that exceeded thresholds for ambient air quality standards. All homes
in that study had gas cooking burners. However, because homes that participated in the study
(dubbed the Healthy Efficient New Gas Homes study) were large, that raised the question of
whether the results apply to smaller homes in which the same emission event produces much
higher concentrations because of less dilution. A study that used a physics-based simulation
model to assess the impacts of using average performance range hoods in a large,
representative sample of homes in Southern California found that a substantial fraction
exceeded the threshold of 100 ppb of NO2 over a one-hour averaging period.
Another question raised by the Healthy Efficient New Gas Homes study was whether combined
OTR microwave/exhaust fan appliances provide performance similar to that of conventional
range hoods. In homes that participated in the study, there were more OTRs (n=38) than
conventional range hoods (n=32), despite there being no OTRs at the time that were certified
to meet airflow requirements of California’s Building Energy Efficiency Standards. There was
also a concern that the method used to measure OTR airflow in the Healthy Efficient New Gas
Homes study may have caused a bias in the results by not including all air inlets .
Venting range hoods help with indoor air quality management only if they are used during
cooking. It is thus important to know how frequently and under what conditions they are
operated during cooking. In many studies, range hood use has been estimated by participant
self-reporting. For example, in a study of 1,448 California houses built in 2003, 28 percent of
respondents reported using a kitchen exhaust fan when cooking with cooktop burners and
only 15 percent reported use when cooking with an oven. In a 2015 web-based survey of
occupants in 2,781 California homes built since 2003, 34 percent reported using range hoods
during cooking always or most of the time, 30 percent reported occasional use, and 32 percent
reported rarely or never using a hood. In another California study, 34 percent of 372 homes
reported using range hoods during cooking with higher frequencies during dinner and more
use with longer cooking duration.

Project Purpose
The overarching aim of this project was to determine whether the provisions of the Building
Energy Efficiency Standards within the California Building Code are sufficient to protect
Californians from pollutants generated during cooking, particularly with gas burners. The
project had four technical tasks:

 3

1. Field study of ventilation and indoor air quality in new and renovated low-income
 apartments;
 2. Analysis of range hood use patterns in homes with gas cooking burners;
 3. Performance of combined over-the-range microwave and exhaust devices;
 4. Pollutant exposure simulations to inform capture efficiency standards.

Project Approach
The objectives of the field study were to assess indoor air quality and the performance of
code-required mechanical ventilation equipment in apartments in which gas cooking burners
are used frequently. The study focused on properties serving income-qualifying tenants in
buildings that were built or renovated under the state’s residential building code requirements
for mechanical ventilation. The researchers developed the study plan to complement the
recent Healthy Efficient New Gas Homes study that focused on single-detached homes built
with code-required ventilation since detached homes are larger with lower occupant densities.
The study first identified qualifying buildings with owners or managers willing to provide the
needed logistical support. The researchers then recruited tenant households through flyers
and other outreach. The project team visited candidate sites to confirm the presence of
compliant mechanical ventilation equipment by inspecting 2-4 unoccupied units.
Researchers surveyed participants to obtain information about satisfaction with air quality and
thermal conditions in the home and routine activities that affect ventilation and indoor air
quality. The project team documented characteristics of mechanical ventilation equipment,
cooking appliances, and thermal conditioning systems and measured unit airtightness and
ventilation equipment airflows. Temperature, humidity, carbon dioxide and air pollutant
concentrations were measured inside each apartment and air pollutant concentrations were
measured outdoors on site. The team installed sensors to monitor use of gas cooking burners,
ventilation equipment, and natural ventilation. The researchers also asked participants to
record occupancy and activities during each day of monitoring. Surveys and activity logs were
collected and equipment was removed after one week of monitoring in each apartment.
The objective of the second technical task was to assess actual range hood use based on
monitoring of cooking activities and range hood operation in occupied homes. The research
team analyzed data collected over weeklong periods in 54 houses and 17 apartments which
were recently constructed or renovated. Data were analyzed to determine the frequency of
range hood use during part or all of the cooking events with a focus on the following
parameters: (1) cooking burner(s) used (cooktop, oven or both); (2) home type (house or
apartment); (3) range hood type (conventional hood or OTR); (4) cooking duration (minutes
of burner use); (5) self-reported usage; and (6) fine particulate matter (PM2.5) emissions
during cooking. The research team also investigated whether the rate of range hood use in a
home was associated with any household or equipment characteristics.
The objective of the third task was to assess whether OTRs, which at the time were not
certified to meet the code specifications, could provide equivalent protection to conventional
range hoods that are minimally compliant with code. After initiation, certified airflow and
sound ratings were published for numerous over the range ventilation units via the Home

 4

Ventilating Institute catalog. The task remained focused on the relative performance of OTRs
and conventional range hoods of similar cost, with a focus on capture efficiency.
The task was also expanded to include an investigation of the bias in OTR airflows reported
from the Healthy Efficient New Gas Homes field study. The research team conducted the
following measurements:
 • Measured airflows of OTRs installed in the research team’s research facility with a fixed
 duct configuration that is a reasonable surrogate for many homes.
 • Validated a new method for measuring airflows for OTRs with multiple air inlets.
 • Measured capture efficiency and sound of OTRs installed as above.
 • Compared capture efficiency vs. airflow relationship of OTRs to standard range hoods
 within similar cost range.
 • Estimated bias of the method used to measure airflow in the Healthy Efficient New Gas
 Homes field study.
The objective of the fourth task was to inform consideration of changes to the Building Energy
Efficiency Standards to specify a required level of range hood capture efficiency, rather than
only focusing on airflow and sound requirements. The analysis sought to determine the
capture efficiency needed to control NO2 emitted from natural gas cooking burners and PM2.5
emitted during cooking regardless of the cooking fuel used, that is, assuming that the same
amount of PM2.5 is produced by the meals considered whether they are cooked with gas,
propane or electric burners.
The researchers assessed the indoor air quality implications of varied range hood performance
levels using computer simulations of pollutant emissions and removal processes to determine
time series of concentrations in homes with cooking. The simulations considered emissions
from cooking and entry of pollutants with outdoor air, and accounted for removal by kitchen
ventilation, continuous dwelling unit ventilation and deposition to surfaces. The simulations
assumed that range hoods are used at least for the duration of all cooking events. Simulations
were conducted in a “Monte Carlo” fashion in which key input parameters were selected from
distributions at the start of the time series calculation for each individual home. Input
parameters included home size and number of bedrooms (used in the assignment of the code-
required dwelling unit ventilation rate), outdoor air pollutant levels, and deposition rates.
Details about the simulation model and parameter distributions are provided in the following
sections.

Project Results
Based on a very limited sample of 23 low-income apartments at four sites throughout
California, findings from the research team’s field study of multiunit buildings for income-
qualifying Californians included:
 • Mechanical ventilation systems in a substantial fraction of apartments may have
 operational deficiencies that affect their performance. These ventilation deficiencies
 likely translate to higher concentrations of air pollutants whose main source is indoor
 emission, compared to concentrations that would occur with operation of ventilation
 that meets the state building code.

 5

• Compared to a group of single-detached houses with code-required mechanical
 ventilation that were examined in a recent study, apartments were more likely to have
 dwelling unit ventilation equipment operating but airflows were generally much lower
 relative to equipment ratings compared to equipment found in houses.
 • Measurements of PM2.5 and NO2 during a week of monitoring in apartments and houses
 suggest that in a substantial minority of homes, concentrations may exceed health-
 based limits set by the United States Environmental Protection Agency and the
 California Environmental Protection Agency for ambient air quality or by the World
 Health Organization for personal exposure. Formaldehyde concentrations were lower in
 apartments than in houses; but still routinely above the chronic reference exposures
 levels set by the California Environmental Protection Agency.
 • Data collected in the apartments affirm prior research showing that use of gas cooking
 burners produces high short-term and weekly time-averaged NO2. While concentrations
 of PM2.5 were similar in apartments and houses with similar levels of cooking, NO 2 was
 much higher in the apartments.
The research team’s investigation of range hood use for 784 cooking events in 71 homes,
including 54 houses and 17 low-income apartments, found:
 • Range hoods were used more frequently in single family houses (36 percent) than in
 the apartments (28 percent).
 • Range hood use by home generally increased with cooking frequency.
 • In both houses and apartments, range hood use increased with cooktop use duration,
 but not with oven use duration.
 • Participants who self-reported frequent use actually used their hoods more frequently;
 however, actual use was much lower than self-reported, with range hoods being used
 only 45 percent and 36 percent of the time in houses and apartments where occupants
 self-reported use of range hoods always, usually, or most of the time.
 • Residents in single family houses used range hoods more often when cooking events
 generated any level of PM2.5. In apartments, residents used the range hood more often
 only if high concentrations of particles were generated during cooking.
Findings from the research team’s investigation of the performance of OTRs included:
 • Airflows measured with a transition that covered both the top and bottom inlets of an
 OTR match those measured at the outlet; this supports the use of this method for field
 studies and potentially also for code enforcement.
 • The airflow measurement method used in the Healthy Efficient New Gas Homes field
 study — in which the top inlet was taped and airflow was measured going into the
 bottom inlet — underestimated OTR airflows, presumably by changing flow dynamics
 inside the hood. Correction factors were determined for the 6 hoods and used to correct
 data for 20 OTRs in the Healthy Efficient New Gas Homes dataset.
 • Airflows of OTRs were similar to range hoods of similar cost, when an adjustment is
 made for the functionality of the microwave (which adds cost).

 6

• Airflows of OTRs not listed in the HVI catalog were similar to those that were listed and
 met the airflow requirements of Standard 62.2, set by the American Society of Heating,
 Refrigerating and Air-Conditioning Engineers (ASHRAE) building performance society.
 • OTR capture efficiency generally increases with airflow, and the trend was consistent
 with capture efficiencies reported for OTRs in previous lab and field studies using the
 same method.
 • OTRs and standard range hoods both have much lower capture efficiencies when
 emissions occur on front vs. back burners and capture efficiency is a function of airflow
 for both types of exhaust devices, and for both front and back burners.
 • The central relationship of capture efficiency to airflow is similar for OTRs and range
 hoods for both front and back burners, but capture efficiencies for range hoods as a
 group were much more variable than capture efficiencies of OTRs when emission occur
 on the front burners.
 • Capture efficiency depends greatly on the specific conditions of the test method.
The research team’s simulation-based study of NO2 and PM2.5 concentrations resulting from
cooking in California new homes while using range hoods with varied performance levels,
found the following:
 • It is possible to provide kitchen exhaust ventilation that, when used routinely, will allow
 cooking to occur safely in homes of all sizes, with either electric or gas burners, and
 considering both acute and chronic exposures to cooking-related air pollutants that
 have established health-based guideline or benchmark levels.
 • To maintain low risk (less than 1 percent) of exceeding the health-based threshold of
 100 ppb averaged over one hour in homes with gas burners, range hoods should have
 the following performance:
 o For homes larger than 1,500 ft2, a capture efficiency measured by the ASTM test
 method of 70 percent or a confirmed (verified or certified) airflow of 180 cfm.
 o For homes with 1,000-1,500 ft2, a capture efficiency of 80 percent or an airflow
 of 250 cfm.
 o For homes smaller than 1,000 ft2, a capture efficiency of 85 percent or an airflow
 of 280 cfm.
 • To maintain low risk (less than 1 percent) of exceeding the health-based threshold of
 25 micrograms/cubic meter PM2.5 averaged over 24 hours, every home should have a
 range hood that minimally meets the following specifications:
 o For homes larger than 1,000 ft2, a capture efficiency of 50 percent or an airflow
 of 110 cfm.
 o For homes with 750–1,000 ft2, a capture efficiency of 55 percent or an airflow of
 130 cfm.
 o For homes smaller than 750 ft2, a capture efficiency of 65 percent or an airflow
 of 160 cfm.
Since pollutants are generated from cooking with any energy source, excluding gas cooking
appliances does not eliminate the need for effective kitchen ventilation. However, as seen from

 7

the requirements noted above, the exclusion of gas effectively mitigates the hazards of
combustion pollutants, principally NO2, and provides more flexibility in kitchen ventilation.

Technology/Knowledge Transfer/Market Adoption (Advancing the
Research to Market)
The project team provided extensive technical support to the codes and standards
enhancement team that was assigned to develop proposals for the 2022 Building Energy
Efficiency Standards and to the CEC standards team as they translated those proposals to
requirements for improved kitchen in the 2022 Building Energy Efficiency Standards. The
research team’s technical support included presenting and serving on a panel at a public
workshop on September 30, 2020 and two memoranda with technical comments submitted to
the public docket; the latter addressed specific questions raised by stakeholders at the public
workshop and by CEC staff. The research team also provided multiple briefings to translate the
research team’s technical papers and analyses to stakeholders, including a builder and several
non-governmental organizations; technical support to other entities that develop or maintain
codes and standards related to kitchen ventilation in efficient residences (including ASHRAE,
Heating Ventilation Institute, and the Association for Home Appliance Manufacturers); and
technical support to other researchers studying air pollutant emissions from residential gas
cooking burners and the resulting exposures to Californians.
The researchers have shared the results of this project with the public principally via technical
reports and papers and presentations at scientific conferences, including:
 • Three papers published in peer-reviewed archival journals. All content is freely available
 to the public via the publications page of Lawrence Berkeley National Laboratory’s
 energy technologies area website (https://eta.lbl.gov/publications).
 • Two datasets published on the open-access Dryad platform.
 • Two Lawrence Berkeley National Laboratory technical reports, which are also available
 via the energy technologies area website.
 • Three papers or extended abstracts in the Proceedings of Indoor Air 2020.
 • Three presentations and one symposium at the Indoor Air 2020 conference.

Benefits to California
There is a substantial body of research demonstrating that use of natural gas cooking burners
without adequate ventilation can relatively commonly result in acute NO2 concentrations inside
kitchens that exceed health-based limits set for outdoor air quality. Particles produced and
emitted during cooking can lead to fine particulate matter concentrations that exceed World
Health Organization guidelines. Effective kitchen ventilation enables Californians to safely cook
in their homes without having to experience hazardous air pollutant exposures.
The public health burden of exposure to NO2 from gas cooking burners and PM2.5 from cooking
is substantial. A 2012 study by Logue et al. of Lawrence Berkeley National Laboratory
estimated annual health costs of $940,000 and 19.2 disability adjusted life years (DALYs) lost
per year per 100,000 people when cooking without range hood use. To estimate benefits, the
research team set the cost of a DALY at $100,000 and assume the following: 85 percent of the
13.6 million Californians live in homes with natural gas cooking; range hoods are used during

 8

35 percent of cooking events; and hoods are 55 percent effective on average. Under this
baseline situation, researchers estimate the benefit of range hood use reducing acute
exposures at about $63 million annually. If capture efficiency is increased to 95 percent, the
total benefit would be $110 million annually for a net benefit of $47 million annually. If range
hood use is doubled with high capture efficiency hoods, the total avoided health costs would
be $220 million or about $160 million incremental benefit. These estimates were developed
from simulations of homes in southern California. The estimate of 55 percent capture was
based on measurements from a 2012 study and the range hood use estimates were
approximated from surveys conducted by Lawrence Berkeley National Laboratory over the past
decade.
Surveys indicate that many Californians feel that their kitchen ventilation equipment is too
noisy or ineffective. Standards that address these performance issues will result in products
that are used more – and thus more effectively – and provide comfort and health benefits to
consumers.
The results of this project helped the CEC formulate and establish science-based performance
requirements that are no more strict than essential for maintaining public safety, leading to
significant but hard-to-estimate cost savings relative to the potential alternative of a more
onerous and restrictive standard that could have occurred in the absence of this work.
There are also substantial benefits to equity and environmental justice as the populations most
harmed by inadequate kitchen ventilation performance standards are those living in smaller
homes, which are disproportionately lower-income Californians.

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10

CHAPTER 1:
Introduction

An airtight envelope is a core element of an energy efficient and resilient residential building.
Reducing uncontrolled air exchange with outdoors reduces heating and cooling loads – in part
because the highest rates of uncontrolled air movement occur when outdoor temperatures are
most different from the desired indoor temperatures – and also reduces the entry of outdoor
air pollution, which is particularly important during wildfire events. For multiunit buildings it is
also important to reduce pathways for air to move between units, as movement within the
building can transfer odors and pollutants as well as impact thermal comfort and energy use.
Reducing air leakage can also reduce outdoor air exchange and consequently reduce dilution
and removal rates for air pollutants generated indoors. The California Building Code addresses
this challenge by requiring mechanical ventilation to be installed in all new construction.
Starting in 2008 California’s Building Energy Efficiency Standards (BEES), commonly referred
to as “Title 24,” have required new homes to have mechanical ventilation that is consistent
with Standard 62.2 of the American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE), a professional society concerned with building performance. Standard
62.2, Ventilation and Indoor Air Quality in Residential Buildings, and the BEES require
minimum airflow rates for dwelling unit ventilation to control long-term exposures to
continuously emitted pollutants, kitchen exhaust ventilation to manage odors, moisture and
both short- and long-term exposures to pollutants from cooking and other activities in the
kitchen, and exhaust ventilation in bathrooms and toilet rooms for odor and moisture control
(California Energy Commission 2008; ANSI/ASHRAE 2019). Both ASHRAE 62.2 and the BEES
are periodically updated in light of new information about performance needs and in
consideration of available technologies and products.
Cooking is among the largest sources of air pollutant emissions inside many homes. Gas
cooking burners produce carbon monoxide (CO), nitrogen dioxide (NO2), formaldehyde
(HCHO) and ultrafine particles and electric burners generate ultrafine particles in substantial
quantities (L. Wallace et al. 2008; Dennekamp et al. 2001; Moschandreas and Relwani 1989;
L. A. Wallace, Emmerich, and Howard-Reed 2004; Mullen et al. 2016; Less 2012; B. C. Singer,
Pass, et al. 2017). NO2 from gas cooking burners may commonly result in indoor
concentrations that exceed the threshold of 100 ppb over one hour that is used in the U.S.
ambient air quality standard (B. C. Singer, Pass, et al. 2017; Logue et al. 2014). Belanger et
al. (Belanger et al. 2013) reported that higher residential exposures to NO2 was associated
with asthma severity. In a meta-review, Lin et al. (Lin, Brunekreef, and Gehring 2013)
reported that gas cooking and higher NO2 exposure were each associated with increased risk
of asthma and higher NO2 was associated with current wheeze. High temperature cooking
activities (for example, frying and broiling) contribute odors and pollutants including hazardous
organic gases, polycyclic aromatic hydrocarbons, and fine and ultrafine particles (Abdullahi,
Delgado-Saborit, and Harrison 2013; Buonanno, Morawska, and Stabile 2009; Fortmann,
Kariher, and Clayton 2001; Fullana, Carbonell-Barrachina, and Sidhu 2004; Seaman, Bennett,
and Cahill 2009; Zhang et al. 2010; Y. J. Zhao and Zhao 2018; Torkmahalleh et al. 2017; Chen
et al. 2020). Higher exposures to these pollutants are associated with adverse health effects

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(US EPA 2009). A study in Hong Kong (Yu et al. 2006) also reported a dose-response
relationship between lifetime exposure to cooking fumes and lung cancer. Both gas burners
and cooking generate water vapor that may contribute to excess indoor moisture and
associated problems if not adequately managed (Liu et al. 2020).
Venting range hoods and combination “over the range” (OTR) microwave/exhaust fans
mounted above the cooktop are designed to remove some fraction of the emitted pollutants to
outdoors before they mix into the air volume of the kitchen and throughout the home. There
are several relevant measures of range hood performance. The two most commonly used, and
the measures for which data are most readily available, are airflow and sound level. These
metrics are measured using standard test procedures published by the Home Ventilating
Institute (HVI Publications 914 and 915) (HVI 2013a; 2013b). HVI certifies and publishes test
results in a free online directory, which includes both standard range hood and OTRs. HVI also
provides guidance on minimum and recommended exhaust hood airflow rates in units of cubic
feet per minute (cfm) per linear foot (lf) of cooking appliance width. For a 30-inch (76.2 cm)
wide range, these translate to minimum and recommended airflows of 100 cfm (47 L/s) and
250 cfm (118 L/s).
Several modeling and experimental studies have examined the performance of range hood use
to reduce cooking-related indoor air pollution (Mullen et al. 2016, 201; B. C. Singer, Pass, et
al. 2017, 201; Logue et al. 2014; Delp and Singer 2012, 201; Rim et al. 2012; B. C. Singer et
al. 2012; Lunden, Delp, and Singer 2015; Y. Zhao and Zhao 2020; Dobbin et al. 2018; O’Leary
et al. 2019). Exhaust devices at the cooktop, including range hoods, OTRs and potentially even
downdraft exhaust devices that pull air down toward an inlet at or near the cooktop, may do
this more effectively than an exhaust fan at the ceiling or upper wall.
A third metric, for which more limited data are available, is capture efficiency (CE). Capture
efficiency is defined as the fraction of contaminants emitted at the cooktop that are directly
pulled into the range hood and exhausted to the outdoors before mixing throughout the
house. A CE of 100 percent means all of the cooking pollutants are exhausted directly to the
outside, and a CE of zero means that none of the cooking pollutants are directly exhausted,
allowing all of them to mix with indoor air. Capture efficiency was first studied decades ago
(for example, (Revzan 1986; Li and Delsante 1996)) and the metric has received increasing
attention since it was used in studies conducted by LBNL in the early 2010s (Delp and Singer
2012; B. C. Singer et al. 2012).
Research conducted by the research team’s group prior to the current project, with range
hoods and OTRs in both laboratory and occupied home installations, found that CE for a given
device depends strongly on airflow, the type of cooking and whether cooking is done on the
front or back burners (B. C. Singer, Pass, et al. 2017, 201; Delp and Singer 2012; B. C. Singer
et al. 2012; Lunden, Delp, and Singer 2015). The research team’s studies also found that CE
varies between devices. And based on just a few OTRs included in the studies, it appeared
that the CE performance of OTRs could be appreciably lower than for range hoods.
Kitchen ventilation requirements traditionally have specified a minimum certified airflow and
maximum certified sound rating at the minimum airflow. For any exhaust device placed over
the cooktop, the requirement is for a minimum of 100 cubic feet per minute (cfm) of airflow at
a maximum sound rating of 3 sones. Kitchen ventilation alternately may be provided with a

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higher airflow intermittent exhaust fan or a continuous exhaust fan in the kitchen. Both
ASHRAE 62.2 and the BEES have required for several years that the airflow of installed kitchen
exhaust ventilation equipment must either be verified by on site measurement or assured
through use of a product that has had its airflow measured and certified by an approved
testing and certification process. (And the approach of using a certified product also requires
ducting that complies with prescriptive requirements.) Until recently, the only organization
approved by the state to certify range hood airflow measurements was the Home Ventilating
Institute, or HVI.
Recognizing that airflow is too coarse and imprecise of a measure for range hood
effectiveness, an effort was initiated in the mid-2010s to develop a standard test method for
range hood capture efficiency. The intent was to establish a testing and certification system
analogous to those existing for airflow and sound. The research to support this effort was
conducted by LBNL (Kim, Walker, and Delp 2018) and the standard was developed through
ASTM, resulting in Method E3087 (ASTM 2018). It is important that this method was
developed to be repeatable and to represent emissions from both the burner which is focused
around the edges, and cooking, which is focused in the centers of burners.
The airflow of a range hood installed in a home can differ from the value published by HVI
because the static pressure in the duct system may be substantially higher than the duct static
pressure in the HVI test. And the effect of higher downstream duct pressures varies based on
the performance curve of the fan and the relationship of airflow to pressure in the duct
system, both of which are non-linear. The HVI test procedure sets a downstream pressure for
the range hood fan operating at its highest setting then measures airflow at other settings
using the same system pressure curve. The ASHRAE 62.2 and California Title 24 standards
require range hoods that move at least 100 cfm or 50 L/s of airflow with a downstream duct
static pressure of 62.5 Pa. Yet the vast majority of range hoods listed in the HVI catalog have
been tested at downstream static pressures of only 25 Pa when the fan is operating at high
speed. This operating condition establishes the relationship between airflow and static
pressure (which is described by the airflow vs. static pressure system curve) for the test
configuration. When the test is performed at “working speed”, which is usually the setting
designed to meet the standard flow requirement of 100 cfm or 50 L/s, the static pressure is
thus much lower than 25 Pa.
The installed sound level can also be higher than the value reported in a standard test,
resulting from vibrations in the duct system or a loose mounting of the hood. However, the
test that provides sound level results in sones cannot be replicated in a field setting.
In consideration of the potential differences between rated and installed airflows, it is
important to collect data on airflows of hoods as installed in homes. A method to conduct
airflow measurements of range hoods and other exhaust (or supply) fans was described by
Walker et al. (Walker et al. 2001). Briefly, the method involves affixing a calibrated fan to the
exhaust (or supply) fan via a transition piece that allows for the differential pressure between
the transition and the room to be measured. The calibrated fan is adjusted to the point that
the pressure between the transition and the room is balanced. At that point, the airflow
through the calibrated fan is matching the airflow through the exhaust (or supply) fan. For
range hoods and OTRs, the challenge is to construct a transition that covers all large air inlets
from the room into the exhaust device.

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